The invention relates to a cutting knife for a cutting head of a trimmer. The cutting knife is comprised of a flat elongate base member that has a longitudinal center axis extending from a first end to a second end of the base member. The base member has longitudinal edges extending at a spacing to the longitudinal center axis from the first end to the second end of the base member. The base member has a first face and a second face between which a center plane is positioned, wherein the faces each are delimited in a first direction transverse to the longitudinal center axis by the longitudinal edges and, in a second direction along the longitudinal center axis, by the first end and the second end of the base member. On the first end of the base member, a fastening contour for mounting the cutting knife on the cutting head is provided. The second end of the base member comprises a free knife end of the cutting knife and a knife edge is formed on at least one longitudinal edge of the base member.
Such cutting knives, referred to on the market also as polycut knives, are generally known and exhibit a good cutting behavior and have a long service life.
There are, for example, three cutting knives arranged about the circumference of a cutting head and are spaced apart from each other in the circumferential direction at the same angular spacing relative to each other, wherein the cutting knives are pivotable about a pivot axis in the cutting plane of the cutting knife. When the cutting head rotates, the cutting knives align approximately radially relative to the rotation axis of the cutting head about the pivot axis and a leading knife edge of the cutting knives engage the material to be cut.
The cutting knife is comprised of a flat elongate base member that has a longitudinal center axis extending from the first end to the second end of the base member. The base member comprises longitudinal edges extending at a spacing to the longitudinal center axis from the first end to the second end of the base member. The base member moreover comprises a first upper face (top face) and a second lower face (bottom face). The faces each extend between the longitudinal edges of the base member in a first direction transverse to the longitudinal center axis and, in a second direction along the longitudinal center axis, from the first end to the second end of the base member. On the first end of the base member, the fastening contour for mounting the cutting knife on the cutting head is provided. The second end of the base member forms a free knife end of the cutting knife. A knife edge is formed on at least one longitudinal edge of the base member.
The cutting head with the cutting knives rotates at a speed of up to 12,000 RPM. In a load-free state, the rotary speed can even be higher. As a function of the rotary speed, the cutting knife that is circulating on a circular path generates a noise that is annoying and irritating, in particular in the load-free state of the cutting head.
The invention has the object to configure a cutting knife for a cutting head of a trimmer in such a way that the noise excitation of the cutting knife is reduced, in particular at high rotary speeds.